A small subpopulation within NINCDS Collaborative Perinatal Project children has been identified as being of mixed black and white parentage. Within the interracial group of matings there is no evidence that genetic or socio-economic differences are related to race of mother (or father). Thus socio-psychological influences, presumable operating through mother-child interactions, can be examined indirectly. Two papers have been published which indicate that, although early childhood differences are wholly negligible, children of white mothers eventually develop positive intellectual differences. A paper analyzing longitudinal differences in early growth rates has now been published.